He's not big nor strong enough to play the 4, and he's not quick enough to play the 3.

I don't think a player hitting jumpers qualifies as having a lot of offensive potential. Question: Does Derrick have any defensive upside/skills? Has he shown improvement with his D? And also, can he create for himself offensively?

He's a 4 who is big enough to play the 4. All he has to do is strengthen in the offseason. He's a 4, without any question.